This invention is directed generally to diaphragm pumps. More specifically, this invention is directed to diaphragm pumps used in the spray application of liquid materials ranging from low to high viscosities.
Diaphragm pumps for dispensing paint and similar materials are known from DE-C1-21 04 783, as well as from DE-A1-30 27 314. These pumps have proven themselves in practice for the handling of low to medium viscosity materials, such as lacquers and paints. However, higher viscosity materials, such as building and flame protection agents, corrosion-protective agents, roof coating materials and the like, cannot be adequately suctioned and supplied to a spray gun by such a pump. This is because, in order to ensure an adequate life span, these pumps can be designed only with short strokes of about 3 to 5% of the working diameter of the diaphragm due to the high number of revolutions per minute of the allocated drive motor, which acts immediately on the main piston. Further, according to DE-C2-30 18 687, these pumps have a short stroke cycle because of the high stroke frequency of 23 to 28 Hz at which the diaphragm is driven by the main piston. A satisfactory suction and flow rate is thus not achieved in the handling of highly viscous materials and therefore the nozzle of the spray gun often fails to achieve a good atomization of the medium being handled.
Therefore, there is a need for a diaphragm pump apparatus of the type described below that will enable a highly viscous media to be pumped and sprayed, and so that the diaphragm has a long lifespan, and so that trouble-free operation of the diaphragm pump apparatus is achieved. The required construction expense and manufacturing costs must be kept low, and the individual components should also be easily accessible, so that they can be changed without difficulty in case of eventual wear. Above all, in contrast to the known diaphragm pump apparatus types, the pump frequency is to be reduced substantially and the stroke of the diaphragm is to be increased to about 10% of the working diameter in order to enable a satisfactory suctioning and pumping of highly viscous materials.